Typically an SCD code 6 error indicates an issue with a tape cartridge or tape drive. I would suggest you try an LTO cleaning cart in the drive to see if this resolves the issue. Once the drive clean is complete, try and re-insert the cartridge that run before the error. If the error 6 happens again, there could be issues with the tape cartridge itself. (simple a faulty cartridge perhaps?)

Let me know how you get on with this and feel free to drop me a message on here if you need more help.